This invention relates to biopsy instruments and methods for taking a biopsy. More specifically, this invention relates to disposable biopsy devices for removing several tissue samples using a single insertion.
In the diagnosis and treatment of breast cancer, it is often necessary to remove multiple tissue samples from a suspicious mass. The suspicious mass is typically discovered during a preliminary examination involving visual examination, palpitation, X-ray, MRI, ultrasound imaging or other detection means. When this preliminary examination reveals a suspicious mass, the mass must be evaluated by taking a biopsy in order to determine whether the mass is malignant or benign. Early diagnosis of breast cancer, as well as other forms of cancer, can prevent the spread of cancerous cells to other parts of the body and ultimately prevent fatal results.
A biopsy can be performed by either an open procedure or a percutaneous method. The open surgical biopsy procedure first requires localization of the lesion by insertion of a wire loop, while using visualization technique, such as X-ray or ultrasound. Next, the patient is taken to a surgical room where a large incision is made in the breast, and the tissue surrounding the wire loop is removed. This procedure causes significant trauma to the breast tissue, often leaving disfiguring results and requiring considerable recovery time for the patient. This is often a deterrent to patients receiving the medical care they require. The open technique, as compared to the percutaneous method, presents increased risk of infection and bleeding at the sample site. Due to these disadvantages, percutaneous methods are often preferred.
Percutaneous biopsies have been performed using either Fine Needle Aspiration or core biopsy in conjunction with real-time visualization techniques, such as ultrasound or mammography (X-ray). Fine Needle Aspiration involves the removal of a small number of cells using an aspiration needle. A smear of the cells is then analyzed using cytology techniques. Although Fine Needle Aspiration is less intrusive, only a small amount of cells are available for analysis. In addition, this method does not provide for a pathological assessment of the tissue, which can provide a more complete assessment of the stage of the cancer, if found. In contrast, in core biopsy a larger fragment of tissue can be removed without destroying the structure of the tissue. Consequently, core biopsy samples can be analyzed using a more comprehensive histology technique, which indicates the stage of the cancer. In the case of small lesions, the entire mass may be removed using the core biopsy method. For these reasons core biopsy is preferred, and there has been a trend towards the core biopsy method, so that a more detailed picture can be constructed by pathology of the disease""s progress and type.
The first core biopsy devices were of the spring advanced, xe2x80x9cTru-Cutxe2x80x9d style consisting of a hollow tube with a sharpened edge that was inserted into the breast to obtain a plug of tissue. This device presented several disadvantages. First, the device would sometimes fail to remove a sample, therefore, requiring additional insertions. This was generally due to tissue failing to prolapse into the sampling notch. Secondly, the device had to be inserted and withdrawn to obtain each sample, therefore, requiring several insertions in order to acquire sufficient tissue for pathology.
The biopsy apparatus disclosed in U.S. Pat. No. 5,526,822 to Burbank, et al was designed in an attempt to solve many of these disadvantages. The Burbank apparatus is a biopsy device that requires only a single insertion into the biopsy site to remove multiple tissue samples. The device incorporates a tube within a tube design that includes an outer piercing needle having a sharpened distal end for piercing the tissue. The outer needle has a lateral opening forming a tissue receiving port. The device has an inner cannula slidingly disposed within the outer cannula, and which serves to cut tissue that has prolapsed into the tissue receiving port. Additionally, a vacuum is used to draw the tissue into the tissue receiving port.
Vacuum assisted core biopsy devices, such as the Burbank apparatus, are available in handheld (for use with ultrasound) and stereotactic (for use with X-ray) versions. Stereotactic devices are mounted to a stereotactic unit that locates the lesion and positions the needle for insertion. In preparation for a biopsy using a stereotactic device, the patient lies face down on a table, and the breast protrudes from an opening in the table. The breast is then compressed and immobilized by two mammography plates. The mammography plates create images that are communicated in real-time to the stereotactic unit. The stereotactic unit then signals the biopsy device and positions the device for insertion into the lesion by the operator.
In contrast, when using the handheld model, the breast is not immobilized. Rather the patient lies on her back and the doctor uses an ultrasound device to locate the lesion. The doctor must then simultaneously operate the handheld biopsy device and the ultrasound device.
Although the Burbank device presents an advancement in the field of biopsy devices, several disadvantages remain and further improvements are needed. For example, the inner cutter must be advanced manually, meaning the surgeon manually moves the cutter back and forth by lateral movement of a knob mounted on the outside of the instrument or by one of the three pedals at the footswitch. Also, the vacuum source that draws the tissue into the receiving port is typically supplied via a vacuum chamber attached to the outer cannula. The vacuum chamber defines at least one, usually multiple, communicating holes between the chamber and the outer cannula. These small holes often become clogged with blood and bodily fluids. The fluids occlude the holes and prevent the aspiration from drawing the tissue into the receiving port. This ultimately prevents a core from being obtained, a condition called a xe2x80x9cdry tap.xe2x80x9d
In addition, many of the components of the current biopsy devices are reusable, such as the driver portions, which control the outer and inner needles. This poses several notable disadvantages. First, the reusable portion must be cleaned and/or sterilized. This increases the time necessary to wrap up the procedure, which ultimately affects the cost of the procedure. In addition, the required clean-up and/or sterilization of reusable parts increases the staffs"" potential exposure to body tissues and fluids. Finally, the reusable handle is heavy, large and cumbersome for handheld use.
A further disadvantage is that current biopsy devices comprise an open system where the tissue discharge port is simply an open area of the device. A surgical assistant must remove the tissue from the open compartment using forceps and place the tissue on a sample plate. This ritual must be followed for every sample and, therefore, multiple operators are required. In addition, the open system increases the exposure to potentially infectious materials, and requires increased handling of the sample. As a practical matter, the open system also substantially increases the clean-up time and exposure, because a significant amount of blood and bodily fluid leaks from the device onto the floor and underlying equipment.
Additionally, when using the current biopsy devices, physicians have encountered significant difficulties severing the tissue. For instance, the inner cutter often fails to completely sever the tissue. When the inner cutting needle is withdrawn, no tissue sample is present (dry tap), and therefore, reinsertion is required. In the case of the Burbank apparatus, the failure to completely sever the tissue after the first advancement of the inner cutter results in a necessary second advancement of the inner cutter. In this event, the procedure is prolonged, which is significant because the amount of trauma to the tissue and, ultimately, to the patient is greatly affected by the length of the procedure. Therefore, it is in the patient""s best interest to minimize the length of the procedure by making each and every attempt at cutting the tissue a successful and complete cut.
Additionally, when using the xe2x80x9ctube within a tubexe2x80x9d type biopsy device, the inner cutter can lift up into the tissue receiving opening during cutting. This lifting causes the inner cutter to catch on the edge of the tissue receiving opening, which ultimately results in an incomplete cut and dulling of the blade, rendering the blade useless.
Also, prior devices often produce small tissue samples. As the inner cutter advances, the cutting edge not only starts to sever the tissue, it also pushes the tissue in front of the cutter. This results in a tissue sample that is smaller than the amount of tissue drawn into the tissue receiving opening.
An additional disadvantage of the prior devices is presented by the complexity of the three-pedal footswitch. Prior devices utilized a three-pedal footswitch; one pedal for advancing the inner cannula, another pedal for retracting the inner cannula, and a third pedal for turning on the aspiration. Operation of the three pedals is difficult and awkward.
These disadvantages become even more significant when using the handheld biopsy device. For instance, the physician must operate the biopsy device and the ultrasound probe simultaneously making it particularly difficult to manually advance of the inner cutter. In addition, when an assistant is required to remove each sample from the open discharge port, use of the handheld device becomes even more awkward. Due to these disadvantages, many physicians have declined to use the handheld models.
This is unfortunate because, some lesions that can signify the possible presence of cancer cannot be seen using the stereotactic unit. In these cases, the doctor must resort to either the handheld device or open surgical biopsy. Due to the difficulties associated with the handheld device, doctors often choose the open surgical biopsy, which is particularly unfortunate because a majority of the lesions that cannot be seen using the stereotactic unit turn out to be benign. This means that the patient has unnecessarily endured a significant amount of pain and discomfort; not to mention extended recovery time and disfiguring results. In addition, the patient has likely incurred a greater financial expense because the open surgical technique is more difficult, time consuming and costly, especially for those patient without health insurance.
The disadvantages of the open surgical technique coupled with the odds that the lesion is benign present a disincentive for the patient to consent to the biopsy. The added discomfort alone is enough to cause many patients to take the risk that the lesion is benign. The acceptance of this risk can prove to be fatal for the minority of cases where the lesion is malignant.
Finally, current vacuum assisted biopsy devices are not capable of being used in conjunction with MRI. This is due to the fact that many of the components are made of magnetic components that interfere with the operation of the MRI. It would be desirable to perform biopsies in conjunction with MRI because it currently is the only non-invasive visualization modality capable of defining the margins of the tumor.
In light of the foregoing disadvantages, a need remains for a tissue removal device that reliably applies a vacuum without becoming plugged with blood and bodily fluids. A need also remains for a tissue removal device that is entirely disposable so that both exposure to bio-hazard and clean-up time are significantly minimized, while convenience is maximized. A further need remains for a tissue removal device that completely severs the maximum amount of tissue without requiring numerous attempts at cutting the tissue. A need also remains for a tissue removal device that is MRI compatible. Finally, a need remains for a biopsy tissue removal device that is completely automated, therefore making the handheld biopsy device a more efficient and attractive option.
The present invention fulfills the aforementioned needs by providing a disposable tissue removal device comprising a cutting element mounted to a handpiece. The cutting element includes an outer cannula defining a tissue-receiving opening and an inner cannula concentrically disposed within the outer cannula.
The outer cannula has a trocar tip at its distal end and a cutting board snugly disposed within the outer cannula. The inner cannula defines an inner lumen that extends the length of the inner cannula, and which provides an avenue for aspiration. The inner cannula terminates in an inwardly beveled, razor-sharp cutting edge and is driven by, both a rotary motor, and a reciprocating motor. As the inner cannula moves past the tissue-receiving opening, the inwardly beveled edge helps to eliminate the risk of catching the edge on the tissue-receiving opening. At the end of its stroke, the inner cannula makes contact with the cutting board to completely sever the tissue. The cutting board is made of a material that is mechanically softer than the cutting edge yet hard enough to withstand the force of the inner cannula.
An aspiration is applied to the inner lumen through an aspiration tube. The aspiration tube communicates with a collection trap that is removably mounted to the handpiece. The aspiration draws the sample into the tissue-receiving opening and after the tissue is cut, draws the tissue through the inner cannula to a collection trap.
In a specific embodiment, both the rotary motor and the reciprocating motors are hydraulic motors. Because hydraulic motors do not require any electrical components, this feature allows all of the components to be fabricated of MRI compatible materials.
In another embodiment, the tissue-receiving opening is formed by opposite longitudinal edges that form a number of teeth. The teeth face away from the cutting board at the distal end of the outer cannula. The teeth help prevent the forward motion of the tissue in the opening as the inner cannula moves forward toward the cutting board. This feature maximizes the length and overall size of the core, ultimately resulting in a more efficient lesion removal.
In another embodiment, the outer cannula incorporates a stiffening element opposite the tissue-receiving opening. This stiffening element aids in maintaining the longitudinal integrity of the outer cannula as it is advanced through the tissue.
In addition to the inwardly beveled edge of the inner cannula, one embodiment incorporates additional features to prevent the inner cannula from rising up into the tissue-receiving opening. A bead of stiffening material may be affixed to the inner wall of the outer cannula, or a dimple may be formed in the inner wall of the outer cannula. The bead, or dimple urges the inner cannula away from the tissue-receiving opening and prevents the inner cannula from catching on the opening.